After looking at different options I managed to successfully run the HDMI Calibration having the following image in the background (but flipped so there was a black square top-left):
The calibration process took not even a second, and although it shows success now, I'm not quite there as to how everything was looking before I messed up.
My current ADC Results are as follows:
1st_Y_GH: 0
1st_Y_GL: 0
1st_Cb_BH: 0
1st_Cb_BL: 0
1st_Cr_RH: 0
1st_Cr_TL: 0
2nd_R_L: 75
2nd_G_L: 75
2nd_B_L: 75
2nd_R_H: 96
2nd_G_H: 96
2nd_B_H: 96
Has anyone run into this problem? Is there a better pattern to run the calibration with? Or perhaps someone can post his ADC results... Any help much appreciated!